Neuropharmacology of verbal perseveration.

In this article we will review available evidence concerning the effects of forebrain catecholaminergic and cholinergic activity on verbal perseveration. The anatomy and physiology of these two major neuropharmacological systems make it likely that they influence speech and language functioning directly as well as the cognitive systems that have an indirect impact on speech and language functions. Both catecholaminergic and cholinergic agents have been shown to influence executive cognitive functions (ECFs) such as "resistance to interference" and "attentional switching" as well as mnemonic encoding and retrieval processes. The ECF effects are most likely mediated by prefrontal cortex; mnemonic processes are mediated by both prefrontal and temporal lobes. Although no full-scale clinical trials on the effects of pharmacological agents on verbal perseveration have been conducted as yet, existing preclinical trials suggest that both presynaptic and postsynaptic dopaminergic agents can reduce perseverative responding by increasing inhibitory control processes. Cholinesterase inhibitors and other cholinergic agents can reduce perseverative responding by reducing verbal intrusions.